1. Field of the Invention
The present invention relates to a method of determining a main deflection settling time for charged particle beam writing, a method of writing with a charged particle beam, and an apparatus for writing with a charged particle beam.
2. Background Art
Along with the development of higher levels of integration in semiconductor devices, the dimensions of their circuit patterns have decreased. Formation of a fine circuit pattern in a semiconductor device requires a highly accurate original artwork pattern (i.e., reticle or mask). Electron beam writing apparatuses, which provide a superior resolution, are used to manufacture such original artwork patterns.
An electron beam writing apparatus of this type is known in which the main deflector and sub-deflector are disposed along the electron beam optical path and used to deflect the electron beam to write a pattern on a workpiece on the stage (see, e.g., Japanese Laid-Open Patent Publication No. 2008-71986). In such electron beam writing apparatus, predetermined voltages are applied to the main deflector and the sub-deflector to move the electron beam. The application of these voltages to the deflectors is not instantly fully accomplished, requiring the apparatus to wait for the settling time, which is the time required for electrical circuits such as deflection amplifiers to stabilize. The above publication discloses a method of optimizing the sub-deflection settling time.
On the other hand, traditionally electron beam writing apparatuses have been able to set a long enough main deflection settling time.
However, the size of sub-deflection regions has been decreased to improve the positional accuracy of writing, thus increasing the number of sub-deflection regions in each main deflection region and hence increasing the number of main deflection operations to be performed on the region. Therefore, an increase in the main deflection settling time may result in reduced throughput of the apparatus.
In view of the above problems, it is an object of the present invention to optimize the main deflection settling time for charged particle beam writing and thereby improve the throughput.